In a number of space surveillance systems, detectors are mounted on a focal plane. The detectors may be of the type which require cooling. The prior art includes the mounting of numerous detectors in an array on a focal plane; and in order to cool the array, heat pipes are mounted to the rear of the array focal plane.
Certain types of detectors require operation at extremely low temperatures. At these temperatures active cryocoolers are strong candidates because of the limited heat rejection per unit area available with passive cryoradiators and the subsequent large required radiator areas. However, all current active cryocoolers for space surveillance systems have less projected operating life than desired. Providing two cryocoolers, with only one operating at a given time, would theoretically double the operating life of a surveillance system. The non-operating cryocooler must be thermally decoupled from a cryogenic loop to prevent excessive heat leakage. Thermal switches based on heat pipe technology have been proposed to permit switching between coolers while preventing heat transfer from a warmer inactive cooler. However, known switches offer inadequate performance.